C.sub.4 plants have high abilities of photosynthesis under the conditions of strong light, high temperature or low CO.sub.2. However, their photosynthesis abilities are largely reduced under low temperature except for those which are adapted to low temperature conditions. Although PPDK (EC 2.7.9.1, that catalyzes the reaction in which AMP, phosphoenol pyruvate and pyrophosphate are produced from ATP, pyruvate and orthophosphate) is one of the important enzymes in C.sub.4 path, its activity is not sufficient with respect to the photosynthesis rate in leaf tissue, so that it is one of the enzymes which determine the rate of CO.sub.2 fixation in C.sub.4 photosynthesis. Further, it has been pointed out simultaneously with the discovery of this enzyme that this enzyme is cold-sensitive. In case of maize PPDK, the enzyme activity has a point of inflection at 11.7.degree. C. This temperature is coincident with the limit temperature of growth of maize. From these, it is thought that PPDK is one of the causes which reduce the photosynthesis rate of C.sub.4 plants at low temperature. Therefore, by improving the cold-sensitivity of PPDK, the limit temperature of growth of maize may be lowered. Flaveria brownii which is a plant belonging to the family Compositae is classified into C.sub.3 /C.sub.4 intermediate type, and it is known that its PPDK is not substantially inactivated by low temperature treatment at 0.degree. C. (Burnell JN: A comparative study of the cold-sensitivity of pyruvate, Pi dikinase in Flaveria species. Plant Cell Physiol. 31, 295-297 (1990)).
By cloning the gene encoding the cold-stable PPDK of Flaveria brownii, and by transforming a plant with the gene, it is expected that resistance to coldness can be given to the plant.